Epoxidation catalyst, its use and epoxidation process in the presence of this catalyst

ABSTRACT

Epoxidation catalyst based on titanium zeolite in the form of extruded granules. Use of this catalyst in the synthesis of epoxides, preferably 1,2-epoxy-3-chloropropane or 1,2-epoxypropane, by reacting an olefinic compound, preferably allyl chloride or propylene, with a peroxide compound, preferably hydrogen peroxide. Process for the preparation of an epoxide, preferably 1,2-epoxy-3-chloropropane or 1,2-epoxypropane, by reacting an olefinic compound, preferably allyl chloride or propylene, with a peroxide compound, preferably hydrogen peroxide, in the presence of the aforementioned catalyst.

This application is a divisional of U.S. patent application Ser. No.09/555,149, filed May 26, 2000 now abandoned which is a 371 ofPCT/EP98/07527 filed Nov. 18 1998.

The present invention relates to epoxidation catalysts, in particularcatalysts based on titanium zeolite. It also relates to the use of thesecatalysts in epoxidation reactions, as well as to epoxidation processesin the presence of these catalysts.

It is known to use catalysts based on titanium silicalite in epoxidationreactions. For example, in patent application EP-A2-0 200 260,microspheres based on titanium silicalite which have a diameter of about20 μm and are obtained by atomization, are used in epoxidationreactions. This known catalyst gives rise to a deactivation phenomenon.Regeneration cycles, requiring handling operations, are thereforenecessary. When these catalysts, with a relatively small diameter, areused in epoxidation reactions it is difficult to isolate them from thereaction medium so that they can be transferred to a regenerationtreatment.

The object of the present invention is to resolve this problem byproviding a novel catalyst which is easy to separate from theepoxidation reaction medium with a view to sending it to a regenerationunit. A further object of the invention is to provide an epoxidationcatalyst which has good mechanical strength, high catalytic activity andhigh selectivity.

Yet another object of the invention is to provide a catalyst which iseasy to use in a fixed or fluidized bed.

The present invention therefore relates to an epoxidation catalyst basedon titanium zeolite, which is in the form of extruded granules. It hasbeen found that such a catalyst has the following combined advantages:

it is easy to separate from the epoxidation reaction medium with a viewto sending it to a regeneration unit,

it has good mechanical strength, high catalytic activity and highselectivity,

it is easy to use in a fixed or fluidized bed.

The term titanium zeolite is intended to mean a solid containing silicawhich has a microporous crystalline structure of the zeolite type and inwhich a plurality of silicon atoms are replaced by titanium atoms.

The titanium zeolite advantageously has a crystalline structure of theZSM-5, ZSM-11 or MCM-41 type. It may also have a crystalline structureof the aluminium-free β zeolite type. It preferably has an infraredabsorption band at about 950-960 cm⁻¹. Titanium zeolites of thesilicalite type are highly suitable, Those satisfying the formulaxTiO₂(1−x)SiO₂ in which x is from 0 0001 to 0.5, preferably from 0.001to 0.05, give good performance. Materials of this type, known by thename TS-1, have a microporous crystalline zeolite structure similar tothat of the ZSM-5 zeolite. The properties and main applications of thesecompounds are known (B. Notari; Structure-Activity and SelectivityRelationship in Heterogeneous Catalysis; R. K. Grasselli and A. W.Sleight Editors; Elsevier; 1991; p. 243-256). Their synthesis has beenstudied, in particular, by A. Van der Poel and J. Van Hooff (AppliedCatalysis A; 1992; Volume 92, pages 93-111). Other materials of thistype have a structure similar to that of beta zeolite or ZSM-11 zeolite.

The term extruded granules is intended to mean grains obtained byextrusion. In particular, the granules are obtained by extruding anextrudable mass containing the titanium zeolite and by cutting theextrudate emerging from the extruder into grains.

The shape of the extruded granules is arbitrary. They may be solid orhollow They may be of round or rectangular cross-section, oralternatively a different cross-section with a greater external surfacearea. Cylindrical shapes are preferred. When they are of cylindricalshape, the extruded granules advantageously have a diameter of at least0,5 mm, preferably of at least 1 mm. The diameter is usually at most 5mm, particularly at most 2 mm. The cylindrical shapes have usually alength of at least 1 mm, particularly of at least 2 mm. Lengths of atmost 8 mm are current, those of at most 4 mm give good results. Thecylindrical shapes having a diameter of from 0.5 to 5 mm, preferablyfrom 1 to 2 mm, and a length of from 1 to 8 mm, preferably from 2 to 4mm are suitable.

The content of titanium zeolite in the catalyst according to theinvention is generally at least 1% by weight, in particular at least 50%by weight. The content of titanium zeolite is most often at most 99% byweight, particularly at most 98% by weight. The catalyst according tothe invention generally contains from 1 to 99% by weight, preferablyfrom 50 to 98% by weight, of titanium zeolite, the remainder consistingof a matrix. This matrix preferably contains a siliceous material.

The catalyst according to the invention can be obtained by a processcomprising:

(a) a step of blending a mixture comprising a titanium zeolite powder,water, at least one binder, at least one plasticizer and optionallyother additives, in order to form a paste,

(b) a step of shaping the paste obtained in step (a) by extrusion, inorder to obtain an extrudate,

(c) a step of drying in order to remove at least some of the water,

(d) a step of calcining in order to remove at least some of the organicresidues present, and comprising a granulation step carried out betweenthe extrusion step (b) and the drying step (c) or after the calciningstep (d), in order to obtain extruded granules.

Step (a) generally consists in mixing a titanium zeolite powder withwater, at least one binder, at least one plasticizer and optionallyother additives until a paste is obtained with a viscosity such that itcan be employed in an extruder. The mixing may be carried out in anykind of mixer or blender. All the constituents of the mixture can bemixed simultaneously. As a variant, the binder, the plasticizer, thewater and, if appropriate, the other additives may be premixed beforethey are added to the titanium zeolite powder. The mixing isadvantageously carried out at room temperature. As a variant, themixture may be cooled during step (a), for example with water. Theduration of step (a) can vary from 5 to 60 minutes.

The particle size distribution of the titanium zeolite powder employedin step (a) can vary greatly. It is preferably characterized by a meandiameter of less than or equal to 10 μm, in particular less than orequal to 5 μm. The mean diameter is generally at least 0.05 μm, inparticular at least 0.1 μm. Diameters of less than 0.05 μm are alsosuitable.

The plasticizer which can be used in step (a) may be a polysaccharidesuch as a starch or a cellulose. Celluloses are highly suitable. By wayof examples of cellulose, mention may be made of methyl cellulose,carboxymethyl cellulose and hydroxyethyl cellulose. Methyl cellulose ispreferred.

The amount of placticizer employed in step (a) can vary greatly. Smallamounts of at least 1% and less than 10% by weight relative to theweight of titanium zeolite employed are recommended because they lead tobetter resistance to attrition in comparison with higher amounts.

The binder which can be used in step (a) may be selected from siliconderivatives such as siloxanes. By way of examples, mention may be madeof methyl siloxane or ethyl siloxane ethers. Silicone resins based onpolymethylsiloxane may also be used. Silicone resins of thepolymethyl/phenylsiloxane type are also suitable. It is also possible touse mixtures of different oligomers of the methylsiloxane type. Thebinder employed in step (a) may be in the form of a powder As a variant,it may be in the form of an aqueous emulsion. It may also be used inliquid form Silicone resins based on polymethylsiloxane in the form of apowder, and mixtures of different oligomers of the methylsiloxane typein liquid form are preferred because they lead to catalysts with highermechanical strength. In the calcining step (d), the binder is convertedinto a material forming the matrix which is present in the catalystaccording to the invention.

The amount of binder employed in step (a) can vary greatly. It iscustomarily at least 3% by weight, in particular at least 5% by weight,relative to the weight of titanium zeolite employed. It is commonly atmost 70% by weight, in particular at most 30% by weight, relative to theweight of titanium zeolite employed. Amounts of from 5 to 20% by weightrelative to the weight of titanium zeolite employed are particularlyhighly suitable because they lead to a better compromise between thecatalytic activity and the mechanical strength in comparison with loweror higher amounts.

Lubricators may also be added to the mixture of step (a). These may becompounds based on paraffin, polyvinylpyrrolidone, polyethylene oxideand polyvinyl alcohol.

Pore-forming substances may also be added to the mixture of step (a).These substances are removed during the calcining step (d) and thusincrease the porosity of the catalyst. Melamine may be mentioned by wayof an example of a poreforming substance. The amount of pore-formingsubstance employed is generally at least 5% by weight, in particular atleast 6% by weight, relative to the weight of titanium zeolite employed.It is customarily at most 35% by weight, in particular at most 14% byweight, relative to the weight of titanium zeolite employed. Amounts offrom 6 to 14% by weight relative to the weight of titanium zeoliteemployed are particularly suitable because they lead to betterresistance to attrition in comparison with higher amounts.

The extrusion step (b) may be carried out in a piston extruder. As avariant, it may be carried out in a screw extruder.

The drying step (c) is advantageously carried out at low drying rates inorder to ensure that the catalyst has a high degree of cohesion. Forexample, predrying at low temperature (for example from room temperatureto 90° C., optionally in combination with infrared or microwaveirradiation) may be carried out first, the temperature may then beraised gradually in order to reach the final drying temperature As avariant, when water can be evacuated rapidly by suitable ventilation,the temperature may be increased at a higher rate. The temperature istypically raised at a rate of 1° per minute. The drying is generallycarried out at a final temperature of at least 400° C. The final dryingtemperature is customarily at most 500° C. Lower temperatures from 100to 400° C. may be suitable when the drying time is long enough, forexample 10 to 20 h.

The calcining step (d) is generally carried out at a temperature of atleast 300° C., in particular at least 400° C. The temperature iscustomarily at most 550° C., in particular at most 520° C. Temperaturesin excess of 550° C. are not recommended because most titanium zeolitescannot withstand such temperatures. The duration of the calcining step(d) must be long enough to make it possible to remove most of theorganic residues originating from the binder and/or the plasticizer.Durations of 60 h are typical. Generally, the duration is at least 50 hand at most 100 h. The calcining step (d) is preferably carried out inan oxidizing atmosphere, preferably in air.

As it is described above, the process comprising steps (a) to (d) and agranulation step can be used to prepare other catalysts in the form ofextruded granules.

The catalyst according to the invention can be used in the synthesis ofepoxides by reacting an olefinic compound with a peroxide compound.

The invention therefore also relates to the use of the catalystdescribed above in these syntheses.

The invention also relates to a process for the preparation of anepoxide by reacting an olefinic compound with a peroxide compound in thepresence of the catalyst described above. The epoxide is preferably1,2-epoxy-3-chloropropane or 1,2-epoxypropane. The olefinic compound ispreferably allyl chloride or propylene. The peroxide compound can bechosen from those containing active oxygen and capable of carrying outepoxidations. Hydrogen peroxide and those peroxide compounds which canproduce hydrogen peroxide under epoxidation reaction conditions aresuitable. The peroxide compound is preferably hydrogen peroxide.

EXAMPLE According to the Invention

In this example, extruded granules containing TS-1 were firstlyprepared. They were then used in the synthesis of epichlorhydrin (EPI)from allyl chloride (ALC) and hydrogen peroxide (H₂O₂).

A TS-1 powder was mixed with:

15.8 g of binder (a silicone resin powder of the polymethylsiloxane typewith an SiO₂ content of 87% after calcining at 500° C.) per 100 g ofTS-1,

4 g of plasticizer (methyl cellulose with a viscosity of 12,000 mPas,the viscosity being measured in aqueous solution at 2% by weight) per100 g of TS-1,

10 g of pore-forming substance (melamine) per 100 g of TS-1,

60 g of water per 100 g of TS-1.

The mixture was then blended at room temperature for 25 min at a rodrotation speed of 50 rpm. The paste obtained was introduced into anextruder fitted with a 1 mm die. The extrudate was dried at 120° C. for15 h before being calcined at 500° C. for 60 h in air with a temperaturegradient of 1° per minute. Having been dried and calcined, the extrudatewas then cut using a granulator to a length of 3 mm. The granulesobtained contain 88% by weight of TS-1 and 12% of siliceous matrixproduced by the calcining of the binder.

In a looped reactor containing a bed of the catalyst obtained above(amount of TS-1 introduced=2% by weight of the reaction medium), areaction medium containing ALC, methanol and H₂O₂ (at 35%) wascirculated in molar proportions ALC/H₂O₂=2, methanol/ALC=7.8. After 2.5h of reaction at 25° C., 89% of the amount of H₂O₂ employed wasconsumed. The selectivity with respect to EPI (the molar ratio betweenthe amount of EPI produced and the sum of the amounts of productsformed) was 99%.

What is claimed is:
 1. A process for producing an epoxidation catalystcomprising: (a) blending a mixture comprising a titanium zeolite powder,water, at least one binder, at least one plasticizer, a pore-formingsubstance and optionally other additives, in order to form a paste, (b)shaping the paste obtained in step (a) by extrusion, in order to obtainan extrudate, (c) drying in order to remove at least some of the water,(d) calcining in order to remove at least some of the organic residuespresent, and comprising a granulation step carried out between theshaping step (b) and the drying step (c) or after the calcining step(d), in order to obtain extruded granules, wherein the pore-formingsubstance is added to the mixture of step (a) in an amount of from 5 to35% by weight relative to the weight of titanium zeolite employed. 2.The process according to claim 1, wherein the titanium zeolite has acrystalline structure of the ZSM-5, ZSM-11, MM-41 type, wherein there ismore than 5% and less than 20% by weight compared to the weight of thetitanium zeolite of the binder which is chosen from silicon derivativesand which is converted into a material forming the matrix of thecatalyst during the calcination.
 3. The process according to claim 1,wherein the titanium zeolite has an infrared absorption band at about950-960 cm⁻¹.
 4. The process according to claim 1, wherein the titaniumzeolite is a silicalite satisfying the formula xTiO₂(1−x)SiO₂ in which xis from 0.0001 to 0.5.
 5. The process according to claim 1, wherein theextruded granules are cylindrical and have a diameter of from 0.5 to 5mm, and a length of from 1 to 8 mm.
 6. The process according to claim 1,wherein the catalyst contains from 1 to 99% by weight, of titaniumzeolite, the remainder consisting of a matrix.
 7. The process accordingto claim 1, wherein the plasticizer is a polysaccharide and the bindercomprises a siloxane derivative.
 8. The process according to claim 7,wherein the polysaccharide is a cellulose selected from the groupconsisting of methyl cellulose, carboxymethyl cellulose and hydroxyethylcellulose and the silicon derivative comprises a siloxane.
 9. Theprocess according to claim 1 wherein the titanium zeolite powderemployed in step (a) has a mean diameter of less than or equal to 10 μm.10. The process according to claim 1, wherein the amount of plasticizeremployed in step (a) is at least 1% and is less than 10% by weightrelative to the weight of titanium zeolite employed.
 11. The processaccording to claim 1, wherein the pore-forming substance is added to themixture of step (a) in an amount of from 6 to 14% by weight.
 12. Theprocess according to claim 1, wherein the pore-forming substancecomprises melamine.
 13. A process for producing an epoxidation catalystcomprising: (a) blending a mixture comprising a titanium zeolite powder,water, at least one binder, at least one plasticizer, a pore-formingsubstance and optionally other additives, in order to form a paste, (b)shaping the paste obtained in step (a) by extrusion, in order to obtainan extrudate, (c) drying in order to remove at least some of the water,(d) calcining in order to remove at least some of the organic residuespresent, and comprising a granulation step carried out between theshaping step (b) and the drying step (c) or after the calcining step(d), in order to obtain extruded granules, wherein the pore-formingsubstance comprises melamine.